Thing is… that I don’t recall seeing seamless floors that large anywhere.
With any kind of coating, you would need to have some crevices left for thermal expansion of the material, otherwise it will be covered in cracks in one or two seasons.
If you want to keep it modular, just add a tiny normal map gutter on the edges. In most cases it will be enough.
Additionally, the difference in final picture will be far less extreme than graybox one.